This invention relates to a method of and apparatus for contouring a surface of a workpiece. More particularly, it relates to a method of and apparatus for machining a preselected contour in a surface of a generally cylindrical workpiece.
Particularly in the manufacture of a nuclear nozzle, it is necessary to contour a flat surface of the nozzle. A nuclear nozzle is generally cylindrical and has a flat end face, a nozzle portion, a body portion extending between the flat end face and nozzle portion, and thick walls defining an opening extending through the length of the nozzle. To mount the nozzle on a hollow, cylindrical device for delivering fluid from the device through the nozzle, the end face of the nozzle is generally mated with the cylindrical body portion of the device surrounding a fluid delivery opening made through the device body portion. To prevent ineffective mating of the nozzle with the device, the flat end face of the nozzle is contoured for a better sealing.
In the past, it has been known to contour the end face of the nozzle by duplicating the contour in a pre-prepared wood pattern or cam. A wood cam having essentially the same size and shape dimensions as the nozzle to be machined was first made. The cam was made so that its end face had the contour to be machined into the end face of the nozzle. The nozzle and cam were then mounted on one or more lathes for rotation about their respective longitudinal axes. A tracing mechanism was then placed in contact with the contoured end face of the cam, essentially parallel with the cam's longitudinal axis, and a cutting tool was positioned for cutting the end face of the nozzle, also essentially parallel with the nozzle's longitudinal axis. The tracing mechanism and cutting tool were electrically and/or mechanically connected, so that any movement of the tracing mechanism was mimicked by the cutting tool. Upon rotating the cam and nozzle and operating the tracing mechanism to follow the contour of the cam end face, the cutting tool similarly moved to cut the cam contour into the nozzle. Thus, the contour of the cam end face was duplicated in the nozzle end face.
The above described type of contouring operation has several disadvantages. First, if one is manufacturing several nozzles having different dimensions, then several wood cams must be prepared and stored. The difficulty of storage is readily appreciated because these cams and their mandrel are generally about 6 to 9 feet in length and 3 to 6 feet in diameter. Also, although wood may be the best material from which to prepare the cams, upon being stored they may tend to warp, whereby their reliabilty becomes questionable. Second, because of the cam size factor mentioned above, a cutting operation using a wood cam is more costly and less reliable than one in which a cam of the contouring apparatus of the present invention, discussed below, is used. For example, the time expended for arranging a large wood cam on a lathe and the cost of the raw wood from which the cam is made are greater than when the apparatus of the present invention is utilized. Also, it has been found that because of the difference in size between the wood cam and the tracing mechanism, instability or chatter of the tracing mechanism occurs during the tracing operation, which results in error in the contour being machined in the end face of the nozzle.
The apparatus of the present invention overcomes these disadvantages. The contouring apparatus of this invention includes a pattern, a mechanism for detecting changes in selected dimensions of the pattern, a cutting tool, and means for transmitting signals from the detecting mechanism, in response to the changes in the selected pattern dimensions, to the cutting tool for controlling the cutting depth of the tool into the end face of the nozzle being contoured.
The pattern of the apparatus of the present invention is pre-prepared having particular dimensions. However, the pattern of the present invention does not have the same dimensions as either the nozzle to be machined or any end face or surface having the contour to be machined into the end face of the nozzle. In the method of using the apparatus of the present invention, the contour being machined into the nozzle end face is not a duplication or tracing of any contour in the pattern, but rather is a reflection of the changes in selected dimensions of the pattern. Thus, the pattern of the present invention need not have the shape of the nozzle.
As is readily appreciated from the drawings of this invention, the pattern and nozzle are quite different in shape and size. Therefore, the disadvantage of having to make the pattern as large as the nozzle being machined is avoided as are the consequent problems discussed above related to pattern size. It has also been found that the pattern may be made from metal or other materials less expensive and more reliable than wood.
It is therefore an object of this invention to provide an apparatus for and method of contouring that are less expensive and more reliable than those known in the prior art.
Another object of this invention is to provide an apparatus for and method of contouring which require less time for preparation prior to the contouring operation than is presently required.